Cup for the Blind / commodity

Blind people might get scalded when they fetch hot water with cups. Because they cannot see water level, hot water might overflow and scald them. This cup has a vacuum structure like a thermos bottle, which can make an echo sound while water is filled in. With water level rising, the air in the cup reduces and the echo sound goes sharper, which can be told by people easily. This really helps the blind people to “hear” the water level and to know when to turn off the water switch.